Niacinamide is a biologically active form of niacin (vitamin B3) found widely in many root vegetables and yeasts. It is also an important precursor to the co-factors NADH (nicotinamide adenine dinucleotide) and NADPH (nicotinamide adenine dinucleotide phosphate). Along with their reduced forms NADH and NADPH, these enzymes participate in numerous enzymatic reactions and also act as antioxidants. One of the advantages of niacinamide is its stability being unaffected by light, moisture, acids, alkalis, or oxidizers.

Niacinamide has several proposed medicinal applications in the skin including anti-inflammation, prevention of photoimmunosuppression and increased intercellular lipid synthesis.

Mode of Action

Niacinamide’s role as a co-enzyme precursor may explain the multiple roles it has in skin, but this is not clearly defined. Topical niacinamide is described to have several benefits on aging skin including but not limited to improved barrier function, improved appearance of photoaged facial skin (including texture, hyperpigmentation, redness, fine lines and wrinkles) and reduced sebum production. Additionally, niacinamide is believed to influence cutaneous pigmentation by down-regulating transfer of melanosomes from the melanocytes to the keratinocytes without inhibiting tyrosinase activity or cell proliferation, and it may also interfere with the cell-signaling pathway between keratinocytes and melanocytes to decrease melanogenesis.

Studies suggest that niacinamide has no effect on tyrosinase activity, melanin synthesis or melanocyte number in a monolayer culture system. Alternatively, the authors found that niacinamide down-regulated the number of melanosomes transferred from melanocytes to keratinocytes by 35 to 68% in a co-culture model system with 1 mmol L-1 niacinamide for 12 days. Niacinamide with retinyl palmitate has been shown to improve hyperpigmentation and increase skin lightening after 4 weeks of treatment compared with vehicle alone. In a separate clinical study, topical niacinamide was also shown to decrease collagen oxidation products and improve aging-induced yellowing or sallowness. .
The actual process by which niacinamide down-regulates melanosome transfer remains to be properly established.

Safety

The safety and efficacy of niacinamide for PIH in darker skinned individuals has not been studied; however, topical 2 to 5% niacinamide has shown some efficacy when used alone or in combination with N-acetyl glucosamine for the treatment of melasma and UV-induced hyperpigmentation in fair-skinned patients and Asians.